Ballast tamping machine with toggle action tamping mechanism



mm m HI M n HT Fm I T C A April 10, 1962 BALLAST TAMPING MACHINE WITHTOGGLE Filed Jan. 13, 1960 4 Sheets-Sheet 1 INVENTOR. FRANK H. PHILBRICKBY 2 z Aprll 10, 1962 F. H. PHILBRICK 3,028,813

BALLAST TAMPING MACHINE WITH TOGGLE ACTION TAMPING MECHANISM Filed Jan.15, 1960 4 Sheets-Sheet 2 MTV.

April 10, 1962 F. H. PHILBRICK 3, ,8

BALLAST TAMPING MACHINE WITH TOGGLE ACTION TAMPING MECHANISM Filed Jan.15, 1960 4 Sheets-Sheet 3 INVENTOR. Famz H. PHILBRICK MACHINE WITHTOGGLE F. H. PHILBRICK ACTION TAMPING MECHANISM BALLAST TAMPING April10, 1962 Filed Jam. 15, 1960 INVENTOR. FRANK H. PHILBRICK BY g z A-r'rY.

nite

The present invention relates to tie tamping or ballasting machines ofthe general type shown and described in my United States Patent No.2,536,887, granted on January 2, 1951, and entitled Ballast TampingMachine, and, in certain respects, the present invention is anembodiment and adaptation of certain features disclosed in such patent.The invention is also an improvement upon and an adaptation of theballast tamping machine shown and described in my United States PatentNo. 2,482,123, granted on September 20, 1949.

It is among the general objects of the present invention to provide animproved ballast tampin machine of the type shown and described in myabove mentioned United States patents wherein the tamping shoes orelements are positively actuated under the control of a drophead toapply pressure to the ballast and force the same under the ties by apositive impacting thrust, as distinguished from that class of machineswherein a vibratory action of the tamping elements is relied upon toslither the ballast by gravity beneath the ties and into any pockets orvoids which may be present to receive the ballast, and wherein themachine is highly efiicient in packing the ballast under the ties sothat the latter will be raised against the rails and forced into firmcontact with the latter.

Another general object of the invention is to provide an improvedmachine of this character wherein the tamping head and all of the toolswhich are operatively mounted thereon are operatively positioned at thefront end region of the supporting truck therefor and in such a mannerthat the front and rear wheels of the truck may at all times besupported on portions of the railway track whi h are firmly supported onties which previously have been packed with ballast.

The ballast tamping machines shown and described in my two abovementioned patents, as well as certain other machines of this generaltype, rely for their tamping action upon the free fall by gravity of arelatively massive drophead and the motion of the drop-head istransmitted to the tamping elements proper through a cam and levermechanism wherein a change in cam direction is encountered after thetamping shoes have actually entered the ballast. Such direction changein the cam slope takes place near the bottom of the free fall of thedrop-head and it involves the loss of con iderable power which,otherwise, would be applied to the task of forcing the tamping shoesinwardly and beneath the tie. it also involves an appreciable impactforce directly on the machine framework which better could be applied tothe tamping shoes and which results in undesired vibration and shock tothe machine as a whole. More important, however, is the fact that thecam employed for guiding the linkage mechanism which controls theoperation of the tamping shoes is heavy and cumbersome and tends tothrow the machine ofi balance, especially when the drophead ispositioned at the front of the machine and overhangs the front wheels.Still further, the width of the cam structure, particularly at thebottom regions thereof where the direction change takes place. is, ofnecessity, sufficiently great that it precludes positioning the dropheadclose to the front wheels and, as a consequence, the drop-head must bepositioned forwardly of the front wheels an appreciable distance, thusfurther contributing tent 3,028,818 Patented Apr. 10, 1952 towardmachine unbalance and, on occasions, causing the rear wheels to leavethe track.

The present invention is designed to overcome the above notedlimitations that are attendant upon the construction and use ofconventional ballast tamping machines and, toward this end, theinvention contemplates the provision of a machine wherein the cumbersomecam mechanism is dispensed with and, instead, the accelerating motion ofthe drop-head is transmitted to the tamping shoes by a leverage systemalone, such system'involving a toggle action wherein the moment oftamping force applied to the tamping shoes to produce inward pressure onthe ballast tending to force the latter beneath the tie constantlyincreases as the drop-head falls, and as the drop-head approaches itslowermost position, this tamping moment is at its maximum, it havingincreased several fold from the time the tamping shoe enters the ballastuntil its movement is finally arrested by the damping action of theballast against which the tamping force is dissipated.

The provision of a ballast tamping machine of the character brieflyoutlined above being among the principal objects of the invention, astill further and important object is to provide such a machine whereinthe toggle and other linkage is of improved design and is so constructedthat it does not interfere with placement of the drop-head and thesupporting structure therefor close to the front wheels of the machine,thus providing a machine which has an adequate degree of stableequilibrium so that the same will at all times find firm support on thetrack undergoing installation or repair.

It is still another object of the invention, in a machine f this sort,to provide an improved linkage mechanism wherein the path of movement ofthe Working end of the tamping shoe, after it has initially entered theballast, is such that it will follow a more eifective tamping paththrough the ballast than has heretofore been possible with machineshaving cam-operated tamping shoes.

A still further object of the invention is to provide a control linkagefor effecting operation of the tamping shoes and having associatedtherewith means whereby the throw of the tamping shoes associated withthe machine may be adjusted to accommodate different heights of trackrails.

Finally, it is an object of the invention to provide a toggle actionlinkage mechanism for controlling the oper ation of a series of tampingshoes on a ballast tamping machine wherein, although high toggle forcesare applied to the tamping shoes, the linkage mechanism is incapable oflocking itself in a dead-center position so that the drophead is alwayscapable of being readily elevated at the end of each operating cycle.

Numerous other objects and advantages of the invention, not at this timeenumerated, will become readily apparent as the following descriptionensues.

In the accompanying four sheets of drawings forming a part of thisspecification, one illustrative embodiment of the invention has beenshown.

In these drawings:

FIG. 1 is a fragmentary vertical sectional view taken through a portionof the machine framework in the vicinity of the tampinginstrumentalities, showing the tamping elements in their operativeworking position against the ballast;

FIG. 2 is a fragmentary side elevational view of portions of thestructure shown in FIG. 1;

FIG. 3 is a side elevational view similar to FIG. 1 showing the tampingelements in their raised inoperative position; and

FIG. 4 is a fragmentary perspective View of a portion of the machineframework in which the drop-head is guided in its vertical movements.

Referring now to the drawings in detail, the rails of a railway trackare designated at and 11, respectively, and they are supported in theusual manner on ties 12 beneath and around which the ballast 14 isadapted to be packed. The ballast tamping machine of the presentinvention is adapted to be tractionally supported on the rails 10 and totravel therealong in a forward direction as indicated by the arrow inFIG. 1 with the entire weight of the machine being supported on ties 12beneath which ballast 14 has previously been packed or tamped by thetamping instrumentalities 16 associated with the machine. In otherwords, the machine operates upon forward ties to pack the ballasttherebeneath and then travels forwardly in a progressive manner so thatas the tamping instrumentalities seek new ties for tamping purposes, themachine moves onto a portion of the rail which is supported by tieswhich have just been operated upon.

The tamping instrumentalities 16 of the present invention may beoperatively installed on a wide variety of machines of the drop-headtype and the particular machine selected for illustration herein hasbeen fragmentarily shown with only such parts as pertain to the guidingof the drop-head in its vertical movements as well as certain linkagereaction points on the machine framework being illustrated. Otherwise,the machine illustrated herein may be substantially the same as thatshown and described in my Patent No. 2,536,887 referred to above. Theinvention is concerned solely with the tamping instrumentalities and thedrop-head on which they are mounted, at least in part, and with themanner in which these instrumentalities are operated from fixed reactionpoints on the machine framework by relative movement between thedrop-head and framework. For a full understanding of the machine whichhas been only fragmentarily illustrated herein and of the manner inwhich vertical movements are applied to the drop-head, reference may behad to such patent.

The machine on which the tamping instrumentalities 16 of the presentinvention are mounted includes a car truck frame having side framemembers 20 and 22 which are supported upon conventional car wheelassemblies 24, the latter including flanged car wheels 26 designed totravel on the rails 10. Only the front car wheels have been illustratedherein since only the extreme front end region of the machine whichsupports the tamping instrumentalities 16 bears a specific relationshipto the present invention. A portion of the side frame members projectforwardly beyond the forward car wheel assemblies 24 and'may be regardedas a forward extension of the machine framework.

The tamping instrumentalities 16 are operable under the control of adrop-head 30 which extends transversely of the truck framework and ismounted to slide vertically in channel-like guides 32 (FIG. 4) which arefixedly supported in the machine framework. The drop-head 30 carries thetamping elements 34 and functions as a drop hammer for operating theelements to tamp the ballast 1 4 beneath the tie 12 on which the rails10 are laid. The guides 32 are attached to side plates 35 which, inturn, are secured to the side frame members 20 and 22 and which serve toreinforce and brace the vertical guides 32 against verticalmisalignment. The upper ends of the guides are rigidly cross-connectedby channel beams 35 and gusset plates 38 while the lateral ends of theplates 35 are rigidly cross-connected by channel beams 40 and 42. Fromthe above description, it will be seen that the assembly just describedand which forms the disclosure of FIG. 4 provides a rigid cage-likestructure on the machine framework forwardly of the front wheels 26including spaced apart channel beams for the operation between them ofthe drop-head 30 and the various tamping instrumentalities associatedwith the same.

The drop-head 30 is operable by power from an in ternal combustionengine carried by the machine framework through mechanism (not shownherein) which lifts the drop-head throughout a predetermined distanceand then releases it for a drop-hammer stroke, during which stroke thevarious tamping elements 34 are caused to move bodily with the drop-headand, in so moving, they are brought into tamping relation with respectto the tie 12 being treated and with respect to the adjacent ballast 14.The motor and mechanism by means of which the drop-head is thus actuatedand caused to move in its vertical path within the guides 32 forms nopart of the present invention and, for a full disclosure of suchmechanism, reference may be had to my Patent No. 2,536,887 previouslymentioned. Briefly, however, it may be stated that the drop-head 30 israised to the fullest extent of which it is capable of being raised asshown in FIG. 1 by a trip. action wherein certain abutments such as havebeen shown at 50 in FIG. 1 and which are carried by the drophead 16 areengaged by rollers 52 mounted on an endless chain 54. The chain isprovided with a vertical straightaway portion and the various rollers52, as they move upwardly along the straightaway portion pick up theabut ments on one side of the drop-head and apply successive liftingmovements to the drop-head with the rollers releasing the abutments asthey move away therefrom and travel around the uppermost of twosprockets (not shown) on which the endless chain 54 is mounted. As theabutrnents are released, the drop-head will fall by gravity from theelevated position wherein it is shown in FIG. 3 to the lowered positionwherein it is shown in KG. 1.

A gang of the tamping elements 34 are provided at each side of thedrop-head 30. These elements are in the form of elongated first classlevers which are pivoted medially of their ends to the lower region ofthe drophead 30 in a manner that will be described presently. The lowerarm 60 of each element 34 constitutes the tamping shoe or tool proper,while the upper arm 62 constitutes a lever arm forming an element of thetoggle link mechanism by means of which the tamping shoe is actuated.

As best seen in FIG. 2, the drop-head is formed with two pairs of spaceddownwardly projecting lower extensions 64, each pair being disposed onopposite sides of a slot 66. One of the slots 66 is in verticalalignment with the track rail 10 while the other slot is in verticalalignment with the rail 11. The extreme lower end of each extension hasformed thereon a pair of oppositely and laterally extending attachmentears 63. The ears on each side of the drop-head are aligned and each earreceives therethrough a pivot shaft 70 with the shaft projectingcompletely through the ear. The tamping elements 34 are arranged inpairs with one element being disposed on each side of an ear 68 so thatthe ear serves to space the elements of each pair apart. Fastening nuts72 are applied to the threaded ends of the various shafts 70 to maintainthe tamping elements in their pivoted relation relative to the drop-head30. The extreme lower end of each arm 60 is formed with an enlargedtamping head 74 of fork-like design and having a series of downwardlyprojecting tamping fingers 76 associated therewith designed for ballastpenetration and packing in a manner that will be set forth presently.

The tamping elements of the gangs on opposite sides of the drop-head 30are disposed in opposed relationship. These tamping elements move bodilywith the drop-head, rising with the latter during its upstroke anddescending therewith during its downstroke while at the same time thetamping elements on opposite sides of the drop-head 3% swing toward eachother in such a manner that the opposed pairs of arms or tamping shoesproper 60 engage the ballast 14 therebetween and pack the same beneaththe various ties 12.

The actuation of the various tamping elements 34 is effected, accordingto the present invention, under the control of a toggle linkagemechanism including linkage elements certain of which are pivotallyconnected to the drop-head 36, others of which are pivotally connectedto the tamping elements 34, and still others of which are pivotallyconnected to fixed reaction points on the machine framework. Thislinkage mechanism is designed to impart to the various tamping elements34 inward swinging movements of a character which are more effectivethan heretofore has been possible utilizing cam controlled tampingelements, while at the same time, eliminating the use of heavy andcumbersome cam tracks which, by necessity, interfere with the closepositioning of relatively massive drop-head 30 and the front Wheelassemblies 24.

Referring now to all views of the drawings, on opposite sides of thedrop-head 80 a series of raised bosses 80 are formed and each of thesebosses provides a pair of spaced cars 82 between which there extends apivot pin 84. Pivotally attached to each pin 84 is the upper end of anelongated thrust link 86. The lower end of each thrust link 86 isbifurcated as at 88 and the upper enlarged end 91} of a relatively shortthrust link 92 extends between the furcations 94 of the link 86 andreceives therethrough a floating pivot shaft 96. In the embodiment ofthe invent-ion illustrated herein there are two such floating pivotshafts 96 on each side of the drop-head 30, one of which spans the slot66 above the rail and the other of which spans the slot 66 above therail 11. It is within the purview of the invention, however, to providea single elongated pivot shaft 96 on each side of the drop-head 30, suchshaft extending completely through all four of the aligned pairs of ears32.

The lower end of each short thrust link 92 is formed with an enlargement100 which extends between the upper ends of each pair of tampingelements 34 and which is pivotally connected thereto by means of a pivotpin 102. Fastening nuts 1% are received on the threaded ends of the pins162. The medial region of each floating shaft 96 receives thereover thelower end 105 of a guide link 1&6 and the upper end 108 of such link ispivotally connected to a reaction pin 110 which extends between a pairof cars 112 (FIG. 4) welded to a threaded sleeve 114 threadedly mountedfor vertical adjustment on an adjusting screw 116 which passes throughupper and lower plates 118 and 119 carried by one of the channel beams40 or 42, as the case may be. A lock nut 120 serves to maintain thesleeve 114 in any desired position of vertical adjustment.

It is to be noted that the length of the thrust link 86 is slightly lessthan the length of the guide link 106 but appreciably greater than thelength of thrust link 92, and that the combined length of these twothrust links is greater than the length of the guide link 1G6.Additionally, in any position of the drop-head, the length of the guidelink 106 is less than the shortest distance between the fixed reactionpin 110 and a straight line connecting the pivot pin 84 and the pivotpin 102. By such an arrangement, the links 86 and 92 and the tampingelements 34 connected thereto are constrained to move in predeterminedpaths and in a predetermined manner, as will now be described in detail.

In the operation of the tamping mechanism described above, the machinewill be positioned on the rails 10 and 11 so that the tie under whichballast is to be packed or tamped will underlie the drop-head 30 withthe various pairs of opposed tamping elements 34 being disposed invertical planes which straddle the tie forwardly and rearwardly of thetie. With the machine motor in operation, the various rollers 52 carriedby the endless chain 54 will successively engage the abutments 50 on thedrop-head 3t and pick up the drop-head, so to speak, and elevate thesame to the position wherein it is shown in FIG. 3. As the rollers 52move out of the vertical plane of the straightaway portion of theendless chain in passing around the uppermost chain sprocket, theabutments will be released so that the drop-head 30 may fall under theinfluence of gravity toward the position wherein it is illustrated inFIG. 1. During such fall of the drop-head 30, the tamping elements 34will be carried downwardly bodily with the drop-head and, in so moving,the relatively long thrust links 86 will exert -a generally axiallydirected thrust upon the relatively short thrust links 92 tending toforce the upper ends of the arms 68 associated with the tamping elements34 outwardly away from the drop-head 38. As best seen in FIG. 3, whenthe drophead 38 is in its raised position the thrust links 86 and 92extend at a wide obtuse angle to each other. As soon as the drop-head3t} commences its free downward fall, the guide link 1116 will swingoutwardly away from the drop-head, while the thrust link 86 will swinginwardly toward the drop-head, thus causing the floating pivot pin 96 todescribe an arc of a circle. In so moving, the floating pivot pin 96will first apply tension to the short thrust link 92 tending to move theupper ends of the tamping elements 34 inwardly toward the drop-head 30to thus spread the tamping shoes proper 60 outwardly away from eachother and away from the drop-head. This spreading of the tamping shoesproper 60 will allow the same to initially engage the ballast atrelatively widely spaced regions on opposite sides of the particular tie12 undergoing treatment.

The movement of the tamping elements 34 before the same engage theballast is relatively unimportant except insofar as it operates to causethese elements to engage the ballast at widely spaced regions. Movementof the tamping elements 34 after the same have initially engaged theballast is extremely important since the effectiveness of the tampingaction is dependent solely upon the movement of the shoes through theballast. After the shoes 66 have initially engaged the ballast 14, theguide link 3106 has forced the two thrust links 86 and 92 away fromtheir initial approximately aligned position so that the parts assumethe dotted line position shown in FIG. 1 with the links 86 and 92extending at an acute angle from each other. Thereafter, continueddownward move ment of the drop-head 30 causes the link 166 to again tendto straighten out the two links 86 and 92 by a true.

toggle action so that they assume a wide obtuse angle with respect toeach other as previously described and so that a very powerful thrust isapplied to the upper arm.

68 of the tamping element 34 with the extreme tamping end of the shoe 60following the broken line path shown in FIG. 3. In the upper regions ofthe path of movement of the shoe 60 after it has engaged the ballast,the increments of motion of the shoe are substantially vertical so thatthe ballast will be forced downwardly in the roadbed. Subsequently,increasing increments of inward motion are applied to the shoe 60 sothat the ballast will effectively be forced beneath the tie 14. Thevarious links associated with the linkage mechanism just described serveto positively control the motion of the tamping shoes 60 inasmuch asthere is no lost motion involved in this linkage system. The guide link106, upon initial descent of the drop-head 30, effects a rapid breakingof the toggle action near the top of the stroke and a gradualstraightening out of the toggle thrust links 86 and 92 near the bottomof the stroke so that a powerful toggle spreading action is attainedtending to exert extremely high tamping forces on the tamping shoes 60,these forces gradually increasing as the drop-head approaches the limitof its downward movement.

From the above description, it is thought that the construction, use andmany advantages of the herein described ballast tamping mechanism willbe readily apparent. The invention is not to be limited to the exactarrangement of parts shown in the accompanying drawings or described inthis specification as various changes in the details of construction maybe resorted to without departing from the spirit of the invention. Forexample, while these tamping instrumentalities have been illustratedherein in connection with a machine embodying a single drop-head 30, theprinciples of the invention are equally applicable to machines of thetype having split or separately operable drop-heads, in which case eachdrop-head or section thereof will embody a mechanism such as has beenillustrated in FIG. 1. Only insofar as the invention has particularlybeen pointed out in the accompanying claims is the same to be limited.

Having thus described the invention what I claim as new and desire tosecure by Letters Patent is:

l. In a machine for tamping ballast etween and beneath the ties of arailway track, in combination, a supporting framework having wheelsmounted thereon for travel along the two rails comprising said track, adrophead designed for vertical alignment with a tie about which ballastis to be tamped, a pair of opposed guideways on opposite sides of theframework respectively and within which said drop-head is verticallyslidable between an elevated and a lowered position, a pair of opposedtamping elements pivotally mounted on opposite sides of the drop-headfor swinging movement about respective horizontal axes intermediate theends of the elements, each element including a lower arm presenting atamping tool proper and an upper lever arm, a thrust link pivotallyconnected to said lever arm, a thrust link pivotally connected to thedrop'head, the free ends of said thrust links being pivotally connectedtogether, a guide link pivotally connected at one end thereof to saidthrust links at the point of pivotal connected therebetween, the otherend of said guide link being pivotally connected to a fixed reactionpoint on said framework, and means for raising said drop-head to itselevated position and for thereafter releasing it.

2. In a machine for tamping ballast between and beneath the ties of arailway track, the combination set forth in claim 1 including,additionally, means for regulably adjusting the vertical height of thereaction point to which said other end of the guide link is pivotallyconnected.

3. In a machine for tamping ballast between and beneath the ties of arailway track, a supporting framework having wheels mounted thereon fortravel along the two rails comprising said track, a drop-head designedfor vertical alignment with a tie about which ballast is to be taniped,a pair of opposed guideways on opposite sides of the frameworkrespectively and within which said drop-head is vertically slidablebetween an elevated and a lowered position, a pair of opposed tampingelements pivotally mounted on opposite sides of the drop-head forswinging movement about respective horizontal axes intermediate the endsof the elements, each element including a lower arm presenting a tampingtool proper and an upper lever arm, a thrust link pivotally connected tosaid lever arm, a thrust link pivotally connected to the drop-head, thefree ends of said thrust links being pivotally connected together, aguide link pivotally connected at one end thereof to said thrust linksat the point of pivotal connection therebetween, the other end of saidguide link being pivotally connected to a fixed reaction point on saidframework which is spaced from the drop-head a distance less than thelength of said guide link, said drop-head being formed with a clearancevoid therein to accommodate the swinging movement of said guide link andthrust links during movement of the drop-head, and means for raisingsaid drop-head to its elevated position and for thereafter releasing it.

4. In a machine for tamping ballast between and beneath the ties of arailway track, the combination set forth in claim 3 including,additionally, means for regulably adjusting the vertical height of thereaction point to which said other end of the gmide link is pivotallyconnected.

5. In a machine for tamping ballast between and beneath the ties of arailway track, a supporting framework having wheels mounted thereon fortravel along the two rails comprising said track, a drop-head designedfor vertical alignment with a tie about which ballast is to be tamped, apair of opposed guideways on opposite sides of the frameworkrespectively and within which said rop-head is vertically slidablebetween an elevated and a lowered position, a pair of opposed tampingelements pivotally mounted on opposite sides of the drop-head forswinging movement about respective horizontal axes intermediate the endsof the elements, each element including a lower arm presenting a tampingtool proper and an upper lever arm, a first thrust link pivotallyconnected to said lever arm, a second thrust link pivotally connected tothe drop-head, the free ends of said thrust links being pivotallyconnected together, a guide link pivotally connected at one end thereofto said thrust links at the point of pivotal connection therebetween,the other end of said guide link being pivotally connected to a fixedreaction point on said framework which is spaced from the drophead adistance less than the length of said guide link, said drop-head beingformed with a clearance void therein to accommodate the swingingmovement of said guide link and thrust links during movement of thedrop-head, the length of said first thrust link being slightly less thanthe length of said guide link and the combined lengths of said firstthrust link and second thrust link being greater than the length of saidguide link, and means for raising said drop-head to its elevatedposition and for thereafter releasing it.

6. In a machine for tamping ballast between and be neath the ties of arailway track, the combination set forth in claim 5 including,additionally, means for regulably adjusting the vertical height to whichthe reaction point to which said other end of the guide link ispivotally connected.

7. In a machine for tamping ballast between and beneath the ties of arailway track, a supporting framework having wheels mounted thereon fortravel along the two rails compirsing said track, a drop-head designedfor vertical alignment with a tie about which ballast is to be tamped, apair of opposed guideways on opposite sides of the frameworkrespectively and within which said drophead is vertically slidablebetween an elevated and a lowered position, a pair of opposed tampingelements pivotally mounted on opposite sides of the drop-head forswinging movement about respective horizontal axes intermediate the endsof the elements, each element including a lower tamping shoe portion andan upper lever arm, a first thrust link pivotally connected to the leverarm, a second thrust link pivotally connected to the drop-head, the freeends of said first and second thrust links being pivotally connectedtogether, a guide link pivotally connected at one end thereof to saidthrust links at the point of pivotal connection therebetween, the otherend of said guide link being pivotally connected to a fixed reactionpoint on the framework which is spaced from the drophead a distance lessthan the length of the guide link, said drop-head being recessed toaccommodate the swinging movement of said guide link and thrust linksduring move ment of the drop-head, the length of said first thrust linkbeing less than the length of said guide link and the combined lengthsof said thrust link and second thrust link being greater than the lengthof said guide link, the length of said first thrust link beingappreciably greater than the length of said second thrust link, thelength of said guide link being greater than the shortest distancebetween said fixed reaction point and a straight line connecting thepoint of pivotal connection between the drop-head and first thrust linkand the point of pivotal connection between the second thrust link andlever arm in any position of the drop-head, and means for raising saiddrophead to its elevated position and for thereafter releasing it.

8. In a machine for tamping ballast between and beneath the ties of arailway track, a supporting framework having wheels mounted thereon fortravel along the two rails comprising said track, a drop-head designedfor vertical alignment with a tie about which ballast is to be tamped, apair of opposed guideways on opposite sides of the frameworkrespectively and within which said drophead is vertically slidablebetween an elevated and a lowered position, a pair of opposed tampingelements pivotally mounted on opposite sides of the drop-head forswinging movement about respective horizontal axes intermediate the endsof the elements, each element including a lower tamping shoe portion andan upper lever arm, a first thrust link pivotally connected to the leverarm, a second thrust link pivotally connected to the drop-head, the freeends of said first and second thrust links being pivotally connectedtogether, a guide link pivotally connected at one end thereof to saidthrust links at the point 1 of pivotal connection therebetween, theother end of said guide link being pivotally connected to a fixedreaction point on the framework which is spaced from the drophead adistance less than the length of the guide link, said drop-head beingrecessed to accommodate the swinging movement of said guide link andthrust links during movement of the drop-head, the length otsaid firstthrust link being less than the length of said guide link and thecombined lengths of said first thrust link and second thrust link beinggreater than the length of said guide link, the length of said firstthrust link being appreciably greater than the length of said secondthrust link, and means for raising said drop-head to its elevatedposition and for thereafter releasing it.

References Cited in the file of this patent UNITED STATES PATENTS2,536,887 Philbrick Jan. 2, 1951 FOREIGN PATENTS 66,292 France Mar. 26,1956 (1st addition to 1,076,144)

OTHER REFERENCES Bundesbahn: 1,017,639, printed Oct. 17, 1957 (K1 19a)(German application) 30/20 1 sht. dwg.--2 pgs. spec.

